Between December 2014 and June 2015, more than 33 million chickens, turkeys and ducks were suffocated to death with firefighting foam and carbon dioxide in the midwestern states of Iowa, Minnesota and elsewhere in the US, in response to the avian influenza outbreaks that began on poultry farms in 2014.  Since June, the number of birds exterminated has grown by many millions more in the US and globally. The concentration of billions of highly stressed, immunocompromised birds living in filth, misery and fear across the Earth guarantees that avian influenza outbreaks and epidemics will continue to occur. 
In addition to using firefighting foam and carbon dioxide to exterminate poultry flocks, the US Department of Agriculture supports exterminating them by shutting off the ventilation in the houses and letting the birds bake to death - a process that can take anywhere from half an hour to 3 or more hours for every bird to die. Shutting off the ventilation in the computer-controlled houses is the cheapest method of extermination. Neither gas nor foam is needed. 
Shooting hoses filled with carbon dioxide into the confinement houses, metal boxes and "kill carts" causes the birds to burn, freeze, and suffocate to death simultaneously - and slowly. This is the egg industry's main method of exterminating "spent" hens, whether from battery cages or cage-free confinement operations, with or without bird flu. 
As for fire-fighting foam, which the US Department of Agriculture approved in 2006, contrary to the lie that the birds are dead within a minute of being blanketed under the foam, Bruce Webster of The University of Georgia told a USDA meeting in June 2006: "You saw a lot of escape behavior for 4 to 6 minutes. You saw the birds' heads sticking out of the foam." Eventually, their movements ceased, as the birds were "worn out" with their "volitional struggle," Webster told attendees including myself at the meeting. 
In a firefighting foam trial with turkeys, birds were reported flapping under the foam for up to 6 minutes. This does not mean that the turkeys were unconscious or dead when the flapping stopped or appeared to stop. And foam-covered birds cannot vocalize their suffering. They cannot be seen or heard. Necropsies showed hemorrhages in the tracheas of birds who died under the foam, and "occlusion of the trachea by the foam" was cited by Ruth Newberry of Washington State University as "a serious welfare concern."
A petition is currently being circulated urging the US Department of Agriculture to not bake chickens, turkeys and ducks to death in response to bird flu epidemics. The USDA needs to hear from us.  Only, please understand: there is no humane solution to the mass extermination of "poultry." In the US, birds used in food production are not even covered by the Humane Methods of Slaughter Act, which means they are not recognized under this law as sentient or as having an existence at all. And even if they were covered (as logically they should be), it wouldn't help them in the actuality of the slaughterhouse situation. If you're still wondering whether chickens are fully sentient beings and you want to understand the culture in which they are trapped, please watch this video and share it with your family and friends. (WARNING: Disturbing content) 
In the 21st century, the human consumption of animal products is the greatest weapon of mass destruction on Earth. The human palate for animal products is eating up rainforests, exterminating wild animals and habitats, ruining oceans, hurting birds, fish, and mammals, and supporting slaughter cultures of total sadism. But let us not be hopeless. This is the moment to confront the carnage with a big, fat "No." This is the time to stop feeling guilty about making other people feel guilty for wrecking the lives of animals and the Earth for the sake of an appetite that is all the worse given the abundance of animal-free foods that are available to us. And you know what? If suddenly, this minute, all animal products vanished from the restaurants and supermarkets to be replaced with the smorgasbord of vegan entrees and desserts, people would be happy.  "Oh, this is delicious! I had no idea." It is maddening but energizing to realize this. So let's make it happen.
By Karen Davis, PhD, President of United Poultry Concerns References:
1. Stephanie Strom, "What Do You Do With 33 Million Dead Birds?" New York Times, May 15, 2015, A1. Online headline "Egg Farms Hit Hard as Bird Flu Affects Millions of Hens," May 14, 2015.
2. David Pitt, "USDA: Many factors considered amid disease outbreaks," Associated Press, July 16, 2015.
3. United Poultry Concerns, "Avian Influenza (Bird Flu) - What You Need to Know," 2007.
4. Karen Davis, "Mass Depopulation of Poultry as a Disease Control Method ," July 11, 2006. See also United Poultry Concerns, "Gassing 'Spent' Hens to Death with Carbon Dioxide," January 6, 2015.
5. & 6. Davis, "Mass Depopulation of Poultry as a Disease Control Method."
7. Chris Wolverton, "USDA: Baking Birds Alive is NOT Humane!"
8. Mercy For Animals, "McCruelty Exposed: New investigation reveals birds being clubbed to death for McDonald's Chicken McNuggets,"
9. Visit One Green Planet, VegNews and United Poultry Concerns' Vegan Recipes.